1. Field of the Invention
The present invention relates to a flow path structure to guide fluid such as gas and liquid in various electronic apparatuses.
2. Description of the Related Art
Flow paths such as ducts and conduit pipes that guide fluid such as gas and liquid in a chassis of an electron apparatus are needed to be disposed around various elements in the chassis, so that the flow paths often include a bent portion (curved portion) or a portion whose sectional area is changed in a flow direction of the fluid. Such portions generate, in a direction (or in a plane) orthogonal to the flow direction, difference in flow velocity of the fluid flowing in the flow path. In other words, such portions generate a distribution of the flow velocity.
For example, in a case of providing a fan on a downstream side in a duct inside which air flows, a flow velocity distribution of the air flowing into the fan significantly deteriorates performance of the fan. Moreover, flow of fluid with a flow velocity distribution into a bent portion of the flow path generates flow separation, which decreases utilization efficiency of the flow path. Therefore, acquisition of a high utilization efficiency requires a flow path structure allowing flow of fluid with a uniform flow velocity.
Such a flow path structure is desirable to be employed for, for example, an image projection apparatus such as a liquid crystal projector requiring a miniaturized and low noise configuration while using air convection produced by driving a fan to cool heat generating elements provided inside the projector.
Japanese Patent Laid-Open No. 2002-349944 discloses a flow path structure that rectifies inflow air by a porous plate and a honeycomb plate that are provided at an inlet of a duct including a bent portion, and then introduces the rectified air to an outlet located on a more downstream side than the bent portion through distribution plates provided in the bent portion. This flow path structure further rectifies outflow air by another porous plate and another honeycomb plate that are provided at the outlet.
Moreover, Japanese Patent Laid-Open No. 2005-098657 discloses a flow path structure that provides a flow control filter inside a duct into which air with a flow velocity distribution flows, and that reduces difference in flow velocity by setting a high airflow resistance of the flow control filter for a high flow velocity area and a low airflow resistance thereof for a low flow velocity area. This flow path structure uses a pleated filter as the flow control filter, and increases and decreases the airflow resistance by changing a pleats pitch of the filter.
In addition, Japanese Patent No. 2706222 discloses a flow path structure that provides guide blades formed so as to have mutually similar shapes at a bent portion of a duct. The guide blades allow fluid flowing into the bent portion with a uniform flow velocity to maintain the uniform flow velocity also on a more downstream side than the bent portion.
However, the flow path structure disclosed in Japanese Patent Laid-Open No. 2002-349944 provides the porous plate and the honeycomb plate, which are members significantly increasing flow path resistance, before and behind the bent portion (in other words, at the inlet and the outlet). Therefore, the structure requires increase of power of the fan in order to ensure a predetermined flow rate of the air flowing through the duct, which may increase noise.
Moreover, the flow path structure disclosed in Japanese Patent Laid-Open No. 2005-098657 covers an entire cross section of the flow path orthogonal to a flow direction of the air with the flow control filter, which significantly increases flow path resistance, as with the flow path structure disclosed in Japanese Patent Laid-Open No. 2002-349944, thereby resulting in increase of required power of the fan and noise.
Furthermore, the flow path structure disclosed in Japanese Patent No. 2706222 cannot uniformize the flow velocity of the fluid flowing out from the bent portion if the flow velocity of the fluid flowing in the bent portion is not uniform, that is, if the fluid flowing in the bent portion has flow velocity difference (flow velocity distribution).